Fluid distributors

ABSTRACT

According to one aspect of the present invention a flow distributor comprises a series of fluid switch devices each adapted to receive a respective input flow, coupling paths connecting the devices into a chain, and two common output regions to one or other of which the input flows are routed through the device according to the conditions of the device, the coupling paths being arranged to divert from each device to the next in the chain, a diversionary flow which tends to propagate from the one device to the next the condition prevailing in the former.

D United States Patent 1151 3,661,163

Grant et al. 1 51 May 9, 1972 54] FLUID DISTRIBUTORS 3,093,306 6/1963 Warren ..137 s1.5 [72] Inventors: John Grant, Risley Warrington; Martin may g g Cranfield Bedfmd 3,250,470 5/1966 Grubb... ...235/201 PF g 3,285,264 11/1966 Boothe ..137/81 5 [73] Assi nee: United Kingdom Atomic Energy Authority, 3,338,515 8/1967 Dexter 137/8l.5 X

London, England 3,342,197 9/1967 Phillips.. ..137/81 5 3,410,312 11/1968 Cogar .235/201 PF [22] 3,276,689 10/1966 Freeman 37/815 ux [21] App1.No.: 690,464

Primary E.\amin0r-Samuel Scott [30] Foreign Application Priority Data Almrwy LarsonTaylor & Hmds' D66. 29, 1966 Great Britain ..58,224/66 1 1 ABSTRACT According to one aspect of the present invention a flow dis- C(Ill tributor Comprises a Series of fluid Switch devices each adapted to receive a respective input flow, coupling paths con- [58] Field of Search" 137/815 235/201 necting the devices into a chain, and two common output re- [56] References Cited gions to one or other of which the input flows are routed through the device according to the conditions of the device, UNITED STATES p ATENTS the coupling paths being arranged to divert from each device to the next in the chain, a diversionary flow which tends to 2 h propagate from the one device to the next the condition ru fli in the former. 3,340,885 9/1967 Bauer ..137/81.5 p g 3,468,328 9/1969 Metzger ..137/81.5 2 Claims, 10 Drawing Figures jkT/K \T/ PATENTEDMM 91912 SHEET 3 BF 4 This invention relates to flow distributors. More particularly it utilizes fluid logic (or fluidic) devices whichprovide specific output signals in response to an input signal. In fluidic devices the kinetic energy of a fluid flow is utilized to perform various logic functions similar to those for example, of switches, rectifiers and amplifiers known in the electrical and electronic art. Electronic components often include essential items fabricated from materials which limit the type of environment in which they can be operated. Fluidic devices by contrast do not require such materials and consequently can be used in conditions where the use of electronic devices would not be feasible.

SUMMARY OF THE INVENTION 7 According to one aspect of the present invention a flow distributor comprises a series of fluid switch devices each having at least one stable condition and each adapted to receive a respectiveinput flow, coupling paths connecting the devices into a chain, and two common output regions to one or other of which the input flows are routed through the device according to the conditions of the device, the coupling paths being arranged to divert from each device to the next in the chain, a diversionary flow which tends to propagate from the one device to the next the condition prevailing in the former.

If the switch devices are of a monostable variety, the diversionary flow may be used to sustain an unstable condition in the following device and in this case it becomes possible for all the devices in the chain to be maintained in the unstable condition routing the input flows to the output region which corresponds to this condition. However, this situation relies on all input flows being'maintained and should one or more suffer substantial reduction the switches will all revert to the stable condition and so route the input flows to the other output region.

If the switches are of a bistable variety, it may be arranged that the diversionary flow causes adoption of thecondition in the previous device only when assisted or boosted by a control flow which is added at will or intermittently on an automatic basis, conveniently to all coupling paths simultaneously. In this way, the coupling paths are adapted to serve an AND function and thereby 'it becomes possible to step a given switch device condition down the chain to route the input flows singly and in turn to one of the output regions.

The switching one at a time to a single transmission route may be used for multiplexing fluid flows and so reduce system complexity after the multiplexing stage.

Severe instrumentation design problems arise in the nuclear reactor field where a multiplicity of leads from monitoring or control elements withina reactor pressure vessel have to pass to appropriate control points outside the vessel. To provide access for the leads the pressure vessel must be penetrated by vessel since (to consider only a single benefit) fewer penetrations would be required in the vessel for the reduced numbers of outlet leads. Whereas the temperature and radiation levels associated with present day power reactors are generally too high for electronic components to be used effectively within the vessel and electro-mechanical devices, such as motor driven switches,'may not have an acceptable reliability, the materials and construction of fluid switch devices can readily be made to withstand such severe conditions.

According to another aspect of the present invention a flow distributor is based on a hierarchial array of fluid switch devices. In this array a series of multi-output fluid switch devices constituting a first stage have like outputs connected to a common outputregion through a second stage constituted by at least one further multi-output fluid switch device, atleast two of the like first stage outputs being connectedimparallel to a respective second stage device input and only one ofj-the outputs of such a second stage device being arranged for rout'- ing to the common output region. In. the second stage, leakage represented by switching inefficiency may be diverted away from the route to the common output region. Further stages may be added to increase this effect and so reduce dilution at the output region by unwanted flow components.

DESCRIPTION OF THE'DRAWING Various further aspects of the invention will now be discussed with reference to the accompanying drawings, in which:

FIGS. 1, 2 and 3 are diagrammatic views showing oneparticular form of fluid switch device under variousfluid flow conditions, 3

FIG. 4 is a graph,

FIGS. 5 and 6 are diagrammatic viewsshowing examples of flow distributors using chains of fluid switch devices,

FIGS. 7, 8 and 9 are diagrammatic views showing examples of flow distributors using hierarchial arrays of fluid switch devices, and FIG. 10 is a diagrammatic view showing another example of a flow distributor. F

DESCRIPTIONOF THE PREFERRED EMBODIMENTS In FIGS. 1 to 3 a switch 11 of the bistable Coanda type has an input nozzle 12 and fluid flow output channels 13, 14 dividing from a splitter 15. Control nozzles 16, 17 are disposed on opposite sides of the input nozzle 12. When a jet of fluid atlow velocity issues from the input nozzle 12 it divides at the splitter 15 to flow equally down the two output channels l3, l4. hen

' the jet velocity is increased so that a critical Reynolds Number is exceeded the flow pattern becomes unstable and the ,jet tends to move away from a central position and attaches itself (after the manner described in the so-called Coanda effect) to one or other of the walls to flow out through one output channel 13 as shown on FIG. 1. The jet is held against the wallbya zone of low pressure fluid known as a reattachment bubble I8. By injecting fluid through the control nozzlel6 into the region of the bubble 18, the pressure in this region may be raised causing the jet to switch from flowing down output channel 13 to flowing down output channel 14. The mass flow through output channel 13 may be higher than the input flow (asin FIG. 2) due to induction fromv output channel 14. Alternatively the mass flow through output channel 13 may be lower than the input flow (as in FIG. .3) Since fluid spills overintothe ostensibly unused output channel 14. Thus a fluid sample flowing through a given switch can be diluted and flows ofa combination of switches could interact to provide spurious outputs.

FIG. 4 shows the relationship, for a switch similar tothat of FIG. 1, between the difierential pressure maintained between the output channels of the switch and the ratio of output flow/input flow. Generally it discloses that as the pressure ,differential falls induced flow increases from one outlet channel to the other. In order to reduce the induction and spill-over as previously referred to, the splitter 15, instead .of being sharp, may be made concave towards the inlet nozzle 12in order to promote the setting up of an eddy. between the output channels.

FIG. 5 shows a flow distributor 41 using a chain .of fluid switches (only four of which are shown) to enable a multiplexing method to be applied to a gas cooled reactor (not shown) for the measuring of coolant channel temperatures .(eachof which would normally be monitored by a separate thermocouple). The four illustrated switches 42q, 142b,, 42c, 42d. are similar to the switch described in connection with'FIGS. l,- 2 and 3, preferably modified by the provision .of concave shaped splitter described above. Input flows to the switches are supplied from reactor coolant channels 43a, 43b, 43c, 43d. The right hand output channel (respectively channels 44a-d) of each switch 42a-d is connected to a common sampling line 45 which leads to a common output region represented by a chamber 46 having in it a single thermocouple 47. Sampling is controlled by fluidic AND gates 48a-d.

The first input to each of the AND gates 48a-d is by way of link lines 49a-d, each extending respectively from the previous switch in the chain. The second input to each of the AND gates 48a-d is by way of control lines 50a-d each extending respectively from a common control line 51. Operation of the distributor 41 is as follows: with only the switch 42a in the sampling position and no fluid pulses being transmitted along the common control line 51, coolant from channel 43a passes through switch 420 and along output channel 44a to the sampling line 45 and so to the chamber 46 where the thermocouple 47 can be used to monitor the coolant temperature. If a pulse is now applied along common control line 51, the AND gate 48a will now receive an input along control line 50a in addition to the fluid bleed flow already existing along link line 49 a from output channel 44a. The gate 48a will consequently provide an output fluid pulse which will act to switch the first switch 42a off and to switch the second switch 42b on. Thereafter coolant flow from the channel 43b will be fed to the chamber 46 for temperature monitoring in place of the previous flow from channel 43a. A further control pulse along line 51 will trip the ring to sample channel 436 by way of switch 42c and so on until the sampling returns to channel 430 and switch 420.

Although the distributor described above in connection with FIG. 5 is directed particularly to temperature measurement the thermocouple 47 could be replaced by an appropriate detector for any intrinsic property of the fluid flowing therethrough. In this context, by intrinsic property, is meant any property of the fluid flow which depends on the nature of the fluid rather than the amount of fluid present. Thus for a flow distributor for burst fuel cartridge detection the thermocouple 47 of the above embodiment could be replaced by a suitable radiation detector whereby the existence of fission products in the fluid flow could be detected.

A variation on the fluidic multiplexer of FIG. 5 is a channel blockage detector shown in FIG. 6. To avoid high center fuel temperatures, coolant is pumped through a reactor core (not shown) in fine, closely spaced channels, of which there may be several thousand. One limitation is that if a channel blocks, the consequent temperature and flow changes at the core outlet from that channel would be swamped by the effect of neighboring channels and a dangerous hot spot could be developed inside the channel by this blockage. The blockage detector changes the small scale effect of a single channel blockage into a large scale effect by using the energy from unblocked channels to generate a chain reaction, by which the blockage can be detected. To this end there is shown in FIG. 6 a flow distributor comprising a series of fluid switches (of which only Switches 11a to 14a are shown) which by contrast with those previously described, are monostable; their input channels 11b to 14b are respectively fed by coolant gas from separate reactor coolant channels (not shown) by bleed lines 21 to 2.4. The four switches 11a to 14a are each provided with a first output channel, respectively 11c to 14c, and a second output channel, respectively 11d to 14d. Each first output channel 110 to 14 is branched to provide a switching control output to the next switch in the series by way of control lines lle to 14 respectively. Each of control lines a to 13a is also coupled to a common reset line 25 by way of reset lines 10f to 13f respectively. All the first output channels 110 to 140 are orientated so that any fluid flow from them is to a first common output region (not shown) in the direction indicated by arrow A. All the second output channels 11d to 14d are orientated so that any fluid flow from them is to a second common output region (not shown) in the direction indicated by the arrow B. Suitabletransducers (not shown) are provided so that a fluid flow in the direction of arrow A or B from the output channels is detectable. The switches 11a to 144 and the associated lines and channels are all situated within the pressure shell of the reactor.

In operation, with a nonnal flow of coolant in the reactor coolant channels, a bleed of the fluid coolant is fed, by way of bleed lines 21-24, to the switches 11a to 14a of the distributor. The stable position, to which each switch is biassed (by utilizing the Coanda flow effect) is the one passing fluid along the second output channels 11d to 14d (that is to say in the direction indicated by arrow B). This stable position prevails if no control fluid flow is provided by way of control lines 10 to 14e. Such control flow is initially applied by passing a fluid pressure pulse along the common reset line 25. This causes flow in all the bleed lines 21-24 to be switched from the stable position along the second output channels 11d to 14d to the first output channels to 14. Thereafter a flow bleed from flow in each first output channel 110 to 14 acts, by way of control lines lle to 14e, to maintain flow through the next switch in the chain in the non-stable position. Thus, for example, flow through the first output channel of switch 12a helps maintain flow in the first output channel 13c of switch l3a.- Thus, throughout the series of switches, fluid from the reactor is passing by way of, typically, bleed lines 21 to 24 into the fluid flow switches, and out by way of the first output channels 110 to 14 in the direction of arrow A to the first output region for eventual return to the reactor.

In the event of channel blockage occurring a chain reaction switching effect occurs throughout the chain in the following way: If blockage occurs in the reactor channel feeding bleed line 22, flow through switch 120 ceases. Thus the flow bleed from the first output channel 12c along line 122 is cut off and fluid flow through switch 13a, being biassed to do so, trips from the first output channel to second output channel 13d. Thereafter the output of switch trips in the same way and on around the chain until, finally, switch Ila trips. As the switches trip the fluid flowing out of the second output channels 11d to 14d of the switches is detected by the considerable increase of flow in the direction of the arrow B. If necessary, suitable indexing means can be utilized so that the original switch setting off the chain reaction can be determined by virtue of its position during the chain reaction. Thus in this example the switch concerned will be the one after the last in the chain to trip.

The distributor just described has a fail safe characteristic insofar as an energy supply has to be provided to maintain the apparatus in the unblocked channel" indicating state and failure of that energy supply will cause the switches to trip as described above.

Although the device shown uses binary output fluid switches it would also be possible to utilize fluid amplifiers (such as vortex amplifiers) rather than switches whose (varying) output would be an analogue for a given (variable) input.

A hierarchial arrangement of fluid switches is shown in FIGS. 7-9. FIGS. 7 and 8 show a two stage system and FIG. 9 a four stage (binary tree) system. These systems are applicable to the sampling of nuclear reactor coolant channels for the detection of fuel element sheathing failures, commonly known as burst cartridge detection. The samples of channel coolant are subjected to an examination for symptoms of fission products and if they are found to be present a sheathing failure can be inferred. Multiplex sampling in accordance with FIG. 6 is assumed to be carried out on 72 channels. Because switching ratios are sensitive to the differential pressures across the Coanda switch, as shown in FIG. 4, 71 switches in the nonsampling condition would contribute a flow of 0.71 x units into the common sample line, where x is the spill-over as a percentage of total input flow. A spill-over of 5 percent would therefore give a dilution of the sample by a factor of about 3.5 to l. Dilution renders the detection of a single burst cartridge difficult in a large system since it increases the swamping effect provided by surrounding uncontaminated coolant.

Dilution for a given leakage can be reduced by dividing the 72 switches in the chain into groups and sampling the groups.

For example the 72 may be divided into 12 groups each of six switches constituting a first stage. Each group has like switch outputs connected in parallel to a respective one of l2 switches constituting a second stage. These 12 switches are in turn divided into two groups each of six switches similarly connected to two switches, constituting a third stage, two like outputs of this stage being taken to the fission product detector. Estimating the dilution at each stage gives 0.05 x at stage 1, 0.10 x at stage 2, and 0.11 x at stage 3, so for a 5 percent spillover on each switch the final dilution would be 0.5 to 1. Dilution could be reduced further by using more stages. The staging in this case is chosen to allow a fast scanning facility. There are limits to this method of staging since after a certain number of stages, improvements can be had only at the cost of a large number of switches. For example if a ring of 16 switches is to be sampled and each has a leakage L, then all of the stagings shown in FIGS. 7, 8' and 9 may be used. The leakage and the cost in extra elements to attain this leakage are:

No. of extra It is seen that the leakage of the unstaged ring L, is approximately halved by the use of two extra switches (FIG. 7)

but to halve it again requires seven extra switches (FIG. 8), so

there is a diminution in effectiveness as extra switches are added. In general for a ring of K elements the simplest staging is to add two extra switches reducing leakage from (K-l) L to KL/2. The greatest reduction in a single stage is obtained by breaking the ring in R groups of R switches; the leakage is then 2(R-1) L at a cost of R extra switches. The limit of staging is the binary tree of FIG. 9 which gives a leakage of L (log K- 1), at a cost of K-2K( k)" switches, where m log,K. These formulas indicate the savings very roughly, since K and log K are not always ordinal numbers. In practice the staging will also be chosen to take account of natural groupings of sampling points in the system, and for the open ended samples there will be limitations arising from the interconnection of control lines.

Although most of the examples in this specification have been concerned with the nuclear reactor field the techniques described are applicable to many signal transmission problems.

In the further arrangement of FIG. 10 the principle employed is that the direction of the output flow of each switch in the series is determined by a diversionary flow not only from the previous switch but also from itself. If the diversionary flow occurs in a particular switch condition, say the sampling condition, then the diversionary flows will be unequal at a switch in the non-sampling condition when it is preceded by one which is in the sampling condition. This inequality is used to direct a control flow in a condition-changing manner.

More specifically each of the switches 42 a-c has an associated control switch 52 a-c and the coupling paths for the diversionary flows are laid out as already generally described in the preceding paragraph to apply biasses on' the control switches through their control nozzles. The biasses are chosen so that if, for example, switches 42a and 42b are both in the non-sampling condition (that is to say flow to left-hand output channel of switches 42a and 42b) then the flow to control nozzle 53 is greater than that to control nozzle 54 from the previous switch 42a such that if a flow pulse is applied by the control line 51 this pulse is directed into the control switch output channel 55 and so ensures by transmission to the right hand control nozzle of the switch 42b that the condition of this switch remains unaltered. If switch 42a is instead in thesampling condition, the flow to control nozzle 54 is increased to such a degree of inequality in the opposite sense that an applied flow pulse from the control lme 51 will be directed into the control switch output channel 56 and by transmission to the left hand control nozzle of the switch 42b will cause the change of this switch to the sampling condition. The switch 42a is simultaneously changed oppositely and therefore the sampling condition can be propagated stepwise down the switch series.

We claim:

l. A flow distributor comprising: a plurality of bistable fluid switch devices each provided with main fluid flow input means, first and second control flow input means, and first and second fluid flow outlet means to which the main flow can be diverted in response to control fluid flow, the first control flow input means diverting the main flow to said first fluid flow outlet means and the second control flow input means diverting the main flow to said second fluid flow outlet means; means for introducing a main flow of fluid to the main fluid flow input means of each of said fluid switch devices; manifold means for receiving fluid output from a like fluid flow outlet means of each of said fluid switch devices and for conveying the fluid output to a common output region; means to convey a portion of the fluid output of the first fluid flow outlet means of each fluid switch device to the first control flow input means of one other fluid switch device to couple the switch devices in a chain; an AND gate for each switch device included in the means to convey the portion of the fluid output of the first fluid flow outlet means of each said fluid switch device to the switch device coupled thereto, said portion being the first input of said AND gate; means providing a pulsed control flow common to the second input of each of said AND gates; and means connecting the output of each of said AND gates to the second control flow input means of its said switch device as well as to the first control flow input means of the switch device coupled thereto.

2. A flow distributor comprising a hierarchal array of fluid switch devices, each switch device having at least one stable output condition, a respective main fluid flow input and at least one control fluid input, wherein a first stage made up of a group of said fluid switch devices is connected to a common output region by way of a second stage consisting of at least one fluid switch device, at least two of the outputs from different switch devices in the first stage being connected in parallel as main fluid flow inputs to a given second stage switch device and only one output of said given second stage switch device being adapted for routing to said common output region. 

1. A flow distributor comprising: a plurality of bistable fluid switch devices each provided with main fluid flow input means, first and second control flow input means, and first and second fluid flow outlet means to which the main flow can be diverted in response to control fluid flow, the first control flow input means diverting the main flow to said first fluId flow outlet means and the second control flow input means diverting the main flow to said second fluid flow outlet means; means for introducing a main flow of fluid to the main fluid flow input means of each of said fluid switch devices; manifold means for receiving fluid output from a like fluid flow outlet means of each of said fluid switch devices and for conveying the fluid output to a common output region; means to convey a portion of the fluid output of the first fluid flow outlet means of each fluid switch device to the first control flow input means of one other fluid switch device to couple the switch devices in a chain; an AND gate for each switch device included in the means to convey the portion of the fluid output of the first fluid flow outlet means of each said fluid switch device to the switch device coupled thereto, said portion being the first input of said AND gate; means providing a pulsed control flow common to the second input of each of said AND gates; and means connecting the output of each of said AND gates to the second control flow input means of its said switch device as well as to the first control flow input means of the switch device coupled thereto.
 2. A flow distributor comprising a hierarchal array of fluid switch devices, each switch device having at least one stable output condition, a respective main fluid flow input and at least one control fluid input, wherein a first stage made up of a group of said fluid switch devices is connected to a common output region by way of a second stage consisting of at least one fluid switch device, at least two of the outputs from different switch devices in the first stage being connected in parallel as main fluid flow inputs to a given second stage switch device and only one output of said given second stage switch device being adapted for routing to said common output region. 